A safe, accessible and effective topical microbicide could significantly reduce the rate of HIV sexual transmission and potentially save millions of lives. Human monoclonal antibodies (mAbs) have high potency, specificity and an acceptable safety profile, and are leading candidates for inclusion in topical microbicides. The objective of Project 2 is to identify mechanisms by which diverse mAbs targeting different aspects of HIV-1 transmission (4E10, VRCOl, and anti-HSVgD) operate in the cervicovaginal environment. In Specific Aim 1 we will study Mab interactions with vaginal epithelial cells. We will use human vaginal tissue and the MatTek EpiVaginal organotypic tissue model to determine Mab uptake and release pharmacodynamics and kinetics, Mab penetration depth and distribution, effects on proinflammatory cytokines and mediators of innate immunity, and effects of Mab retention by vaginal epithelial cells on HSV and HIV infection. We will also test the effects of cervical mucus and semen on mAb antiviral efficacy in these assay systems. In Specific Aim 2 we will study the effects of mAbs on cell-associated HIV transmission . In Specific Aim 3 we will study ex vivo efficacy of Mabs following vaginal administration to macaques and women. In collaboration with the clinical project, we will also study effects of mapp66 microbicide film use in women on markers of vaginal inflammation and innate immunity. These data, when combined with data from the other IPCP projects and cores, should provide a solid foundation for the advancement Mab-based vaginal microbicides.